Commerce, science and medicine have long recognized the importance of delivery devices manufactured from erodible, agent release, rate controlling polymers. These devices are valuable because they contain a beneficial agent, that as the polymer erodes, is delivered at a controlled rate, and in an effective amount, to the environment of use. A major advance towards satisfying this recognition was met by the unique poly(orthoesters) and poly(orthocarbonates) disclosed in U.S. Pat. No. 4,180,646 issued to inventors Nam S. Choi and Jorge Heller. The new class of polymers disclosed in the patent comprised a polymeric backbone having a repeating unit comprising a hydrocarbon radical and a symmetrical dioxycarbon unit with a multiplicity of organic groups bonded thereto. These polymers have a controlled degree of erosion to innocuous products when in an aqueous or a biological environment. The polymers can be used for releasing a beneficial agent at a controlled rate to an environment of use.
While the above polymers are outstanding and represent a pioneering advancement in the polymer and the delivery arts, and while they are useful for dispensing numerous beneficial agents to an environment of use, there are instances where the rate of erosion of the polymers can be modified to produce a more preferred result. For example, when the polymers are used as implants in an animal environment of use, it may be therapeutically desirable to modify the rate of erosion the polymer. The rate is modified as a means for regulating the amount of drug released per unit time, by the implant over time. It will be appreciated by those versed in the present arts, that in view of the above presentation, if an erosion rate modifier is made available for poly(orthoesters) and poly(orthocarbonates), such a modifier would represent a valuable contribution and also useful improvement in the practicing arts.